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A specialized facility at JPL aimed at aiding robotic missions to icy ocean worlds is also instrumental in the development of safety tests for advanced spacesuits.
As NASA prepares for its Artemis missions to the Moon and anticipates further explorations of the solar system, astronauts will face unprecedented environmental challenges. Addressing the necessity for advanced protective suits, a unique testing chamber named CITADEL (Cryogenic Ice Testing, Acquisition Development, and Excavation Laboratory) at NASA’s Jet Propulsion Laboratory in Southern California plays a pivotal role in ensuring astronaut safety.
CITADEL was designed to ready robotic explorers for the extreme conditions present on icy celestial bodies, like Europa, one of Jupiter’s moons. The facility is now also essential for assessing the durability of spacesuit components, notably gloves and boots, under extreme cold. The NASA Engineering and Safety Center managed a glove testing initiative in CITADEL from October 2023 to March 2024, while boot testing, led by the Extravehicular Activity and Human Surface Mobility Program based at NASA’s Johnson Space Center in Houston, is scheduled from October 2024 to January 2025.
Looking ahead, the CITADEL team plans to modify the chamber for additional tests focused on spacesuit elbow joints, alongside evaluating the longevity of suit fabrics in lunar conditions. This adaptation includes incorporating abrasion testing and simulating lunar regolith, the fine material of the Moon’s surface, into the chamber for the first time.
“At JPL, we have designed robots that have journeyed throughout the solar system,” stated Danny Green, a mechanical engineer spearheading the boot testing. “It’s remarkable to see our capabilities being utilized to support the return of astronauts to the Moon.”
The Artemis III mission will task astronauts with exploring the Moon’s South Pole, an area presenting extreme conditions far more severe than those encountered by the Apollo missions at the equator. These astronauts may spend considerable time within craters that could house essential ice deposits, found in what are known as permanently shadowed regions. These locations are among the coldest in the solar system, with temperatures potentially plummeting to minus 414 degrees Fahrenheit (minus 248 degrees Celsius), temperatures that CITADEL can simulate effectively.
“Understanding the risks astronauts face in these permanently shadowed regions is crucial, particularly for gloves and boots that maintain prolonged contact with frigid surfaces and tools,” noted Zach Fester, an engineer with the Advanced Suit Team at NASA Johnson and technical lead for the boot testing.
Innovative Cooling Techniques
CITADEL resides in the same facility as JPL’s historic 10-Foot Space Simulator. Using compressed helium, the chamber can reach depths of minus 370 degrees Fahrenheit (minus 223 degrees Celsius), surpassing the capabilities of most cryogenic facilities that typically utilize liquid nitrogen. The dimensions of the chamber—4 feet (1.2 meters) in height and 5 feet (1.5 meters) in diameter—allow easy access for engineers to conduct tests.
One of the chamber’s standout features is its four load locks, which enable the insertion of test materials without disrupting the cold, vacuum environment inside. This design facilitates quick alterations during glove and boot testing despite the lengthy preparation required to establish the low temperatures necessary for experiments.
The cooling process is supported by cryocoolers, while aluminum blocks within the chamber simulate tools astronauts might use or the lunar surface they would traverse. Additionally, a robotic arm assists in handling materials, with several visible-light and infrared cameras monitoring the testing processes.
The analyzed gloves represent the sixth iteration of a design used by NASA since the 1980s, known as the Extravehicular Mobility Unit (EMU). Originally tailored for spacewalks aboard the International Space Station, the suits function as individual spacecraft due to their complex design. Testing in the CITADEL environment at minus 352 degrees Fahrenheit (minus 213 degrees Celsius) revealed that the existing glove model would not suffice for the thermal demands of the lunar South Pole. Boot testing results, utilizing a lunar surface suit prototype called the Exploration Extravehicular Mobility Unit, are still pending full analysis.
Beyond identifying weaknesses in current suit designs, the experiments conducted in CITADEL aim to establish standardized, repeatable testing protocols for the next-generation lunar suit being developed by Axiom Space—the Axiom Extravehicular Mobility Unit, slated for use by NASA astronauts during the Artemis III mission.
“This testing aims to determine limits: specifically, how long can a glove or boot endure exposure to the lunar environment?” explained Shane McFarland, the technology development lead for the Advanced Suit Team at NASA Johnson. “We’re looking to quantify existing hardware capabilities to provide essential data to the Artemis suit vendor while also developing a unique test capability for future suit designs.”
Historically, astronauts have participated in thermal tests, where individuals would insert their gloved hands into chilled environments and hold cold objects, sometimes until their skin temperature dropped significantly. While McFarland emphasizes the continued importance of human participation in testing for suit safety, he points out that such methods do not yield the consistent data required for extensive future planning.
To ensure accurate feedback, the CITADEL team has employed a custom-built manikin hand and foot, designed to simulate the physiological response of human extremities. Fluid loops have been created to mimic blood flow, accompanied by numerous temperature and heat flux sensors that track conditions inside gloves and boots during testing.
“Using CITADEL and advanced manikin technology allows us to test design iterations more rapidly and cost-effectively than traditional testing,” stated Morgan Abney, NASA technical fellow for Environmental Control and Life Support, who initiated the glove testing project. “This gives us the opportunity to explore next-generation suit designs more thoroughly and confidently as we edge closer to sending astronauts back to the Moon.”
The Artemis missions promise to enable astronauts to explore the Moon in pursuit of scientific knowledge, stimulate economic advantages, and lay the groundwork for future crewed missions to Mars.
Source
www.nasa.gov